Monday, October 12, 2015

Pests of Azaleas

Azalea foliage appears whitish, silvery or somewhat bleached, what's the problem?  There are three common pests that can cause this appearance: lace bugs, thrips and mites.

Lace bugs have piercing-sucking mouth parts which remove the sap as they feed from the underside of the leaf. This feeding damage detracts from the plants beauty, reduces vigor, and makes the plant susceptible to other problems.
The adults are about 1/8 to 1/4 inch long, with a brownish black coloration to them. But the highly sculptured, transparent wings have a lacy appearance, thus giving the insect its name. The immature stages of the lace bug are flat and oval with spines projecting from their bodies. Another way of identifying the lace bug is the presence of dark droplets of excrement on the undersides of the leaves. 

The following azalea cultivars have resistance to the azalea lace bug: ‘Dawn,’ ‘Pink Star,’ ‘Ereka,’ ‘Cavalier,’ ‘Pink Fancy,’ ‘Dram,’ ‘Seigei,’ ‘Macrantha,’ ‘Salmon Pink,’ ‘Elsie Lee,’ ‘Red Wing,’ ‘Sunglow’ and ‘Marilee.’

Thrips are small, dark colored insects less than  1/20 inch long. They are typically found on the undersides of leaves. Like lace bugs, tiny black specks of excrement on the undersides of the bleached leaves are clues to the presence of thrips.

Mites are tiny pests, related to spiders and have eight legs as opposed to the six on insects. They also have piercing mouth parts which suck the juices of the plant cells and cause a yellow to bronze stippling of the leaf. They are typically found on the underside of the leaf but with heavy infestations; yet mites will feed on the upper surface as well.

Control for all three is similar. Although there are general predators for these pests such as spiders, predatory mites and ladybird beetles, they are not efficient enough to keep these pests in check. Sometimes the pest can be knocked off the plant with a heavy spray of water. Applications of insecticides such as horticultural oils, neem oil and insecticidal soaps can be effective for temporary reduction of the pest population. It is best to apply them when the pest population is low. Thorough cover is essential, covering both the top and the bottom portions of the leaves. Repeated applications at 5-10 days apart, are usually required for good control.